Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$145.59	8.619%	$158.1384	$158.14	$158.15	$158.10
Purchase #2	$175.63	3.695%	$182.1195	$182.12	$182.10	$182.10
Purchase #3	$32.73	3.102%	$33.7453	$33.75	$33.75	$33.70
Purchase #4	$162.25	6.110%	$172.1635	$172.16	$172.15	$172.20
Purchase #5	$191.30	6.121%	$203.0095	$203.01	$203.00	$203.00
Purchase #6	$74.93	10.224%	$82.5908	$82.59	$82.60	$82.60
Purchase #7	$111.43	6.708%	$118.9047	$118.90	$118.90	$118.90
7 purchase totals =	$893.86		$950.6717	$950.67	$950.65	$950.60